Method and apparatus for attaching a crushable carbon fiber reinforced polymer structure to the outer surface of a battery enclosure

ABSTRACT

A battery housing for a traction motor battery of a vehicle is disclosed that includes a plurality of elongated impact absorbing carbon fiber reinforced polymer members attached to the walls of the enclosure. The impact absorbing members may be corrugated members that have ridges and furrows connected by ramp surfaces that define trapezoidal spaces relative to the sides of the enclosure. The ridges are designed to be deformed into the trapezoidal space in the event of an impact to absorb impact forces and protect the battery. The impact absorbing members may be retained by T-shaped guides on the outer surface of the walls of the enclosure or may be adhesively attached to the sides of the enclosure.

TECHNICAL FIELD

This disclosure relates to protective structures for battery enclosuresfor electric vehicle batteries.

BACKGROUND

Electric vehicles use batteries that are enclosed in an enclosure orhousing that is assembled to the vehicle body. The battery may beassembled to the vehicle body at a location that is spaced from thefront, rear and sides of the vehicle. For example, the battery may beassembled below the passenger compartment, in the trunk, in front of thepassenger compartment or in a longitudinally extending tunnel.

The battery must be protected from damage in a collision. The batteryhousing may be tightly packed with lithium ion battery packs or othertypes of battery cells. Deformation of the battery housing is to beavoided to prevent intrusion of the housing into the area housing thebattery cells. Intrusions into the battery housing may rupture ofbattery cells and spill the contents of the battery cells.

When the battery housing is assembled in a central location in thevehicle, e.g. beneath the passenger compartment, limited crush space isavailable between the side of the vehicle body and the batteryenclosure. More crush space is available between the battery enclosureand the front or rear ends of the vehicle. In either situation, there isa long felt and unfulfilled need for an efficient and effectivelightweight structure for absorbing energy from a collision thatminimizes battery enclosure deformation. The structure must have limitedpackage space requirements while providing added stiffness to thebattery enclosure assembly including the impact absorbing structure.

Some approaches to protecting the battery enclosure have proposed addingbeams and cross members on the battery enclosure or extending outboardof the battery enclosure. These approaches add weight to the vehicle andrequire additional space to package the beams and cross members. Addedweight is to be avoided because added weight adversely affects fueleconomy. Increasing packaging space requirements adversely affectsvehicle design freedom.

The above problems and other problems are addressed by this disclosureas summarized below.

SUMMARY

According to one aspect of this disclosure, an enclosure for a batteryis disclosed that includes a plurality of aluminum alloy enclosure wallsdisposed about the battery and a plurality of corrugated impactabsorbing members made of carbon fiber reinforced polymer (CFRP)attached to the enclosure walls. The impact absorbing members have atleast one ridge and a plurality of furrows that define a plurality oftrapezoidal spaces between the impact absorbing members and theenclosure walls.

According to other aspects of the method, each of the impact absorbingmembers may include at least one ridge that is disposed parallel to theenclosure wall. A first ramp surface and a second ramp surface extendfrom the ridge to the furrows on opposite sides of the ridge and towardthe enclosure wall at an angle. The enclosure may further comprise anattachment flange provided on a first side and a second side of theimpact absorbing members that extend parallel to the enclosure walls.The attachment flange on the first side is connected to one of the firstramp surfaces and the attachment flange on the second side is connectedto one of the second ramp surfaces.

The enclosure may further comprise a plurality of T-shaped guidesattached to the enclosure walls that define receptacles for the impactabsorbing members between two T-shaped guides. The T-shaped guidesextend parallel to each other so that each of the attachment flanges ofthe impact absorbing members are disposed between one of the T-shapedguides and one of the enclosure walls. The impact absorbing membersabsorb an impact applied to the enclosure by collapsing into thetrapezoidal spaces and towards the enclosure wall.

According to another aspect of this disclosure, an enclosure for abattery is disclosed that comprises a plurality of planar aluminumenclosure walls disposed about the battery and a plurality of planarimpact absorbing members attached in a face-to-face orientation tosubstantially cover the enclosure walls.

The enclosure may further comprise a plurality of T-shaped guidesattached to the enclosure walls that define receptacles for the impactabsorbing members between two T-shaped guides that extend parallel toeach other. The planar impact absorbing members include a firstattachment flange and a second attachment flange that are disposedbetween one of the T-shaped guides and one of the enclosure walls. Theplanar impact absorbing members may be adhesively attached to theenclosure walls.

According to another aspect of this disclosure, a method is disclosedfor providing an impact absorbing battery enclosure for a battery of avehicle having a battery powered fraction motor. The method comprisesthe steps of: providing a plurality of sides and a top side and a bottomside; assembling all of the sides together about the battery; andassembling a plurality of impact absorbing carbon fiber reinforcedpolymer members to the sides to form an impact absorbing assembly thatencloses the battery enclosure.

According to other aspects of this disclosure as it relates to themethod, the impact absorbing carbon fiber reinforced polymer members maybe corrugated and have at least one ridge and a plurality of furrowsthat define a plurality of trapezoidal spaces between the impactabsorbing members and the sides of the enclosure. Each of the impactabsorbing carbon fiber reinforced polymer members may include the atleast one ridge that is disposed parallel to the side of the enclosureand a first ramp surface and a second ramp surface that each extend fromthe at least one ridge to the furrows on opposite sides of the at leastone ridge. The ramp surfaces extend toward the side of the enclosure atan angle to define a trapezoidal space with the side that the impactabsorbing member is attached. The impact absorbing carbon fiberreinforced polymer members absorb an impact applied to the enclosure bycollapsing into the trapezoidal spaces and towards the side of theenclosure.

According to other aspects of the method, the method may furthercomprise the steps of providing an attachment flange on a first side anda second side of the impact absorbing carbon fiber reinforced polymermembers that extend parallel to the side of the enclosure and connectingthe attachment flange on the first side and on the second side to one ofthe sides of the enclosure.

The method may further comprise providing a plurality of T-shaped guideson the side of the enclosure that define receptacles for the impactabsorbing carbon fiber reinforced polymer members between two T-shapedguides that extend parallel to each other. Each of the attachmentflanges of the impact absorbing carbon fiber reinforced polymer membersmay be inserted between one of the T-shaped guides and one of the sidesof the enclosure.

The above aspects of this disclosure and other aspects are describedbelow with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic bottom plan view of a vehicle illustrating abattery enclosure disposed on the vehicle frame beneath the passengercompartment.

FIG. 2 is a perspective view of a first embodiment of a batteryenclosure including corrugated carbon fiber reinforced polymer (CFRP)impact absorbing members provided on the sides and top of the enclosure.

FIG. 3 is a fragmentary enlarged perspective view of a portion of thebattery enclosure illustrated in FIG. 2.

FIG. 4 is a fragmentary cross-sectional view of a portion of the batteryenclosure illustrated in FIG. 2.

FIG. 5 is a perspective view of a second embodiment of a batteryenclosure including planar carbon fiber reinforced polymer (CFRP) impactabsorbing members provided on the sides and top of the enclosure.

FIG. 6 is a fragmentary enlarged perspective view of a portion of thebattery enclosure illustrated in FIG. 5.

FIG. 7 is a fragmentary cross-sectional view of a portion of the batteryenclosure illustrated in FIG. 5.

FIG. 8 is a graph of battery case deformation comparing the twodifferent embodiments of the battery case having impact absorbingmembers made according to FIGS. 2 and 5, respectively.

DETAILED DESCRIPTION

The illustrated embodiments are disclosed with reference to thedrawings. However, it is to be understood that the disclosed embodimentsare intended to be merely examples that may be embodied in various andalternative forms. The figures are not necessarily to scale and somefeatures may be exaggerated or minimized to show details of particularcomponents. The specific structural and functional details disclosed arenot to be interpreted as limiting, but as a representative basis forteaching one skilled in the art how to practice the disclosed concepts.

Referring to FIG. 1, a vehicle 10 is diagrammatically illustrated with abattery 12 for a battery-powered traction motor. The vehicle 10 includesa body 14 that is supported on a frame 16. A traction motor 18 is alsoassembled to the frame 16. The traction motor 18 is a battery-poweredtraction motor that is powered by the battery 12 to drive the wheels 20.The body 14 includes a side body 22, a front bumper 24 and a rear bumper26. The battery 12 is shown to be centrally located underneath thepassenger compartment of the vehicle 10. It should be noted that thereis a substantially greater amount of space between the battery and thefront and rear bumper 24 and 26 compared to the relatively closerspacing of the side body 22 to the battery 12. Side impact collisionsthat result in driving the side body 22 toward the battery 12 present agreater challenge when designing impact absorbing elements for thebattery 12 due to the reduced amount of crush space available betweenthe side body 22 and the battery 12.

Referring to FIGS. 2-4, a first embodiment of the battery enclosure,generally indicated by reference numeral 28, is shown to include abottom wall 30 (shown in FIG. 1) and a top wall 32. A front wall 36faces the front bumper 24 (shown in FIG. 1) and a rear wall 38 faces therear bumper 26 (shown in FIG. 1). The battery enclosure 28 includes aright side wall 40 and a left side wall 42. The side walls are joined atcorners 44.

Impact absorbing members, generally indicated by reference numeral 46,are ribbed or corrugated carbon fiber reinforced polymer (CFRP)attachments 46 to the battery enclosure 28. The corrugated CFRPattachments 46 have alternating furrows 48 and ridges 50. The furrows 48are planar areas that are adjacent to one the enclosure walls (38 inFIG. 4). The ridges 48 are planar areas that are spaced from one theenclosure walls. The ridges 50 and furrows 48 are connected by rampsurfaces 52 and 54 on a first and a second side of each ridge 50. Theridges 50 and furrows 48 define trapezoidal spaces 55 between the impactabsorbing members and the enclosure walls.

The corrugated CFRP attachments 46 include carbon fiber reinforcingfibers that are oriented to extend substantially in the directioncorresponding to the length of the corrugated CFRP attachments 46. Thecarbon fibers are oriented to extend parallel to the ridges 50 andfurrows 48. The CFRP attachments substantially cover (understood to beat least 90% coverage) the sides of the enclosure. The carbon fibers areencapsulated in a polymer resin to form the corrugated CFRP attachments46. In one example, the corrugated CFRP attachment may have a thicknessof 2.0 mm.

T-shaped guides 56 are either assembled to the walls of the enclosure 28or integrally molded with the walls of the enclosure 28. The T-shapedguides 56 are disposed to be parallel to the next adjacent T-shapedguides 56. The furrows 48 may be partially received between theenclosure wall and T-shaped guides, as shown in FIG. 4, to retain theimpact absorbing members 46 on the enclosure 28. The portions of thefurrows 48 that are received by the T-shaped guides may be referred toas attachment flanges 58. In one example that was tested in asimulation, the enclosure and T-shaped guides may be 1.0 mm thickaluminum alloy, such as AL6061-T6 and had a mass of 27 kg.

Referring to FIGS. 5-7, a second embodiment of the battery enclosure,generally indicated by reference numeral 60, is shown to include abottom wall 30 (shown in FIG. 1) and a top wall 62. A front wall 66faces the front bumper 24 (shown in FIG. 1) and a rear wall 68 faces therear bumper 26 (shown in FIG. 1). The battery enclosure 60 includes aright side wall 70 and a left side wall 72. The side walls are joined atcorners 74.

Impact absorbing members, generally indicated by reference numeral 76,are planar carbon fiber reinforced polymer (CFRP) attachments 76 to thebattery enclosure 60. CFRP attachments 76 include carbon fiberreinforcing fibers that are oriented to extend substantially in thedirection corresponding to the length of the corrugated CRFP attachments76. The carbon fibers are encapsulated in a polymer resin to form thecorrugated CRFP attachments 76. In one example, the corrugated CFRPattachments 46 may have a thickness of 2.0 mm. The CFRP attachments 46substantially cover (understood to be 90% coverage) of the sides of theenclosure.

T-shaped guides 78 are either assembled to the walls of the enclosure 60or integrally molded with the walls of the enclosure 60. The T-shapedguides 78 are disposed to be parallel to the next adjacent T-shapedguides 78. In one example, the enclosure and T-shaped guides may be 1.0mm thick aluminum alloy, such as AL6061-T6 and had a mass of 27 kg. astested.

The impact absorbing members 76 may be partially received between theenclosure wall and T-shaped guides, as shown in FIG. 7, to retain theimpact absorbing members 46 on the enclosure 28. In one example, theenclosure and T-shaped guides may be 1.0 mm thick and formed of analuminum alloy. Alternatively, the planar impact absorbing members maybe adhesively attached to the enclosure walls.

Referring to FIG. 8, a graph illustrates the battery case deformation inmillimeters over time. A simulated test result for a base steel batteryenclosure made of 1.5 mm HSLA 450 steel having a mass of 52 kg as testedand was compared to each of the two embodiments described above. Thetest results for the embodiment illustrated in FIG. 2-4 with corrugatedCFRP, of the battery enclosure 28 and shows that battery casedeformation resulted in a maximum simulated battery deformation ofslightly less than 75 mm over a period of 15 ms. The simulated testresults for the embodiment illustrated in FIG. 5-7 of the batteryenclosure 60 resulted in a maximum deformation of approximately 85 mmover a period of about 15 ms. Both of the battery enclosures 28 or 60resulted in a marked reduction of battery case deformation compared tothe base steel battery enclosure without the impact absorbing members 46(or 76) that projected about 440 mm of crush over a period of 80milliseconds.

The embodiments described above are specific examples that do notdescribe all possible forms of the disclosure. The features of theillustrated embodiments may be combined to form further embodiments ofthe disclosed concepts. The words used in the specification are words ofdescription rather than limitation. The scope of the following claims isbroader than the specifically disclosed embodiments and also includesmodifications of the illustrated embodiments.

What is claimed is:
 1. An enclosure for a battery comprising: aplurality of aluminum alloy enclosure walls disposed about the battery;and a plurality of corrugated impact absorbing members formed of carbonfiber reinforced polymer attached to at least one of the enclosure wallsthat have at least one ridge and a plurality of furrows that define aplurality of trapezoidal spaces between the impact absorbing members andthe enclosure walls, wherein each of the impact absorbing membersincludes at least one ridge that is disposed parallel to the enclosurewall and a first ramp surface and a second ramp surface that each extendfrom the at least one ridge to the furrows on opposite sides of the atleast one ridge and toward the enclosure wall at an angle, wherein anattachment flange is provided on a first side and a second side of theimpact absorbing members that extend parallel to the enclosure walls,wherein the attachment flange on the first side is connected to one ofthe first ramp surfaces and the attachment flange on the second side isconnected to one of the second ramp surfaces, and wherein a plurality ofT-shaped guides are attached to the enclosure walls that definereceptacles for the impact absorbing members between two T-shaped guidesthat extend parallel to each other, wherein each of the attachmentflanges of the impact absorbing members are disposed between one of theT-shaped guides and one of the enclosure walls.
 2. An enclosure for abattery comprising: a plurality of walls attached to the battery; aplurality of T-shaped guides attached to the walls; and a plurality ofcorrugated members having ridges and furrows defining trapezoidal spacesbetween the ridges and walls, wherein each corrugated member has flangeson opposite sides that are received between two of the T-shaped guidesto retain the corrugated member on one of the walls.
 3. The enclosure ofclaim 2 wherein the ridges of the corrugated members are parallel to thewall and a first ramp surface and a second ramp surface extend from theridges to the furrows on opposite sides of each ridge and toward thewall at an angle.
 4. The enclosure of claim 3 wherein the flanges areprovided on a first side and a second side of the corrugated members andextend parallel to the walls, wherein the flange on the first side isconnected to one of the first ramp surfaces and the attachment flange onthe second side is connected to one of the second ramp surfaces.
 5. Theenclosure of claim 4 wherein the T-shaped guides define receptacles forthe corrugated members between two of the T-shaped guides and areparallel to each other, wherein each of the flanges of the corrugatedmembers are disposed between one of the T-shaped guides and one of thewalls.